The present invention relates to liquid ejection apparatuses in which liquid is retained in a container, supplied to a liquid ejection head through a liquid supply needle having a liquid outlet line, and then ejected to an ejection object.
By way of example, an inkjet recording apparatus will be described as follows. The inkjet recording apparatus has a pressure chamber for pressurizing ink. The ink is then ejected from nozzles to a recording paper, or the ejection object, as ink droplets. Printing data is thus recorded on the recording paper. In the apparatus, printing problems may me caused by vaporization of solvent of the ink from nozzle openings, which may increase the viscosity of the ink, solidify the ink, and allow dust deposition in the nozzle openings, and bubbles trapped in the pressure chamber. Therefore, a capping device is deployed for preventing such vaporization by sealing the nozzle openings when printing is not performed. More specifically, a pump unit generates negative pressure in the capping device and the negative pressure is applied to the nozzle openings for forcibly discharging the ink from the nozzle openings. In other words, the pump unit performs cleaning by forcibly drawing the ink with the increased viscosity and the dust from the nozzle openings by the negative pressure generated in the capping device.
Further, for improving color printing quality, some recording apparatus may use eight types of ink, which are dark and light types of magenta, cyan, yellow, and magenta.
In these cases, ink cartridges must be provided in a quantity sufficient for the eight color inks. This may result in an excessive total weight of a carriage if the apparatus is an on-carriage type in which the ink cartridges are installed in the carriage. It is thus necessary to increase the power of the motor for driving the carriage. Further, relatively great reactive force may be generated in the carriage when the carriage is returned.
To solve these problems, the ink cartridges may be received in a cage-like body attached to the recording apparatus. The ink is supplied from each of the ink cartridge to a recording head serving as the liquid ejection head through an ink supply tube. For maintaining the apparatus as a whole in a well-proportioned state in terms of the weight, it is desired that four of the eight ink cartridges be provided at a lateral end of the apparatus with the remaining four arranged at the opposing end.
In this apparatus, which is called an off-carriage type, the ink in each of the ink cartridges is pressurized to a predetermined level for reliably sending the ink from the ink cartridge, or a liquid container, to the recording head.
Further, if the recording apparatus tilts laterally with the ink cartridges installed therein while, for example, being moved to a different position, water head pressure with respect to the recording head is raised in the group of the ink cartridges located at the affected end of the apparatus. In this case, if each ink cartridge does not have a liquid absorption member formed by a porous body, the ink may leak from the nozzle openings of the recording head.
A recording apparatus described in Japanese Laid-Open Patent Publication No. 5-185603 includes an ink cartridge having a hollow ink supply needle extending from the body of the recording apparatus. When the ink cartridge is installed in the recording apparatus, the ink supply needle is inserted in and projects from the ink cartridge. The interior of the ink supply needle defines an ink outlet line. The ink outlet line of the ink supply needle is connected to a recording head through an ink supply line defined by, for example, a tube. The ink is thus supplied to the recording head through the ink supply needle and the ink supply line.
In this apparatus, a control valve is provided in the ink supply line extending from the outlet line of the ink supply needle to the recording head, for preventing the ink from leaking from nozzle openings of the recording head. The control valve is closed when the recording apparatus is moved or the ink cartridge is installed in or removed from the apparatus. The ink is thus stopped from leaking from the nozzle openings or the ink supply needle.
However, in a state transitional from an open state to a closed state of the control valve, or when the opening degree of the control valve is decreasing, the body of the control valve moves in such a manner as to restrict the communication area of the ink supply line. This causes the ink to flow back from the control valve to the ink supply needle. In this state, if the ink cartridge is separated from the ink supply needle, the ink in the outlet line of the ink supply needle is pressed by the body of the control valve that is being closed. The ink thus drops, or leaks, from an inlet port of the ink supply needle. The ink may contaminate the portion of the recording apparatus in the vicinity of the ink supply needle. Further, the ink may flow into small gaps defined in the recording apparatus.